Adrenoceptors and sympathomemtics Essay Example | Topics and Well Written Essays - 500 words

Adrenoceptors and sympathomemtics - Essay Example In the vascular and smooth muscle cell, the alpha-2 adrenergic receptors are located in the postsynaptic terminal. Most of ÃŽ ± 1-adrenoceptors activation are linked to excitation of postsynaptic target ÃŽ ±-2-adrenoceptors usually activates the Gi inhibitory protein that in turn decreases cAMP. The inhibitory function of alpha-2 adrenergic receptors is vital negative feedback system to control of the discharge of presynaptic nerve terminal’s noradrenaline. These prevent prolonged activation of the effector organs such as male sex organs, eyes and veins (Bryant, Knights and Salerno, 2010, p. 209). These alpha-adrenergic receptors usually control the vasoconstriction of arterioles in skin, pupil dilation, gut relaxation and smooth muscle relaxation in the prostrate and bladder neck. Classification of beta-adrenergic receptors into ÃŽ ²1, ÃŽ ²2 and ÃŽ ²3 considers their affinity to agonist or antagonist. Location of site that recognises agonist and antagonist is in the portion of receptor that is membrane-bound. Distribution of Beta-adrenergic receptors is in various tissues. Beeta-1 is in the heart, beta-2 in the smooth muscle and beta-3 in adipocytes cell membrane (Bryant, Knights and Salerno, 2010, p. 210). All of the beta-adrenergic receptors lead to activation of adenylyl cyclase in which the agonists leads to formation of cAMP from ATP. Activation these receptors leads to increase heart beat rate, relaxed bronchus and uterine and vasoconstriction of arterioles supplying blood to skeletal muscle. Sympathomimetic drugs are those designed to act similarly like adrenaline or noradrenaline by their action on adrenoceptors and act in sympathetic stimulation of the system (Bertram and Anthony, 2009, p. 128). The classification of these drugs as direct or indirect agonist depends on their mode of action in stimulation of the neural